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How to prove transitivity in Fitch. Is it Ok?

| 1. a = b
| 2. b = c
| 3. c = c  =Intro
| 4. a = c  =Elim: 3, 2
| 5. b = c  =Elim: 4, 1
  • I made an edit adding some formatting. You may roll this back or continue editing. You can see the versions by clicking on the "edited" link. Welcome to this SE! – Frank Hubeny Sep 15 '18 at 14:05
  • Line 3 is unneeded, and line 4 is where you should stop (and its by =Elim: 1,2). – Graham Kemp Sep 20 '18 at 5:21
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I was not able to get the proof as you presented it to work in the fitch-style proof checker I am using.

However, the following did work using equality elimination (=E).

enter image description here

The proof checker you are using may be different and the result could require other steps.


References

Kevin Klement's JavaScript/PHP Fitch-style natural deduction proof editor and checker http://proofs.openlogicproject.org/

P. D. Magnus, Tim Button with additions by J. Robert Loftis remixed and revised by Aaron Thomas-Bolduc, Richard Zach, forallx Calgary Remix: An Introduction to Formal Logic, Winter 2018. http://forallx.openlogicproject.org/ Wikipedia, "Fitch notation" https://en.wikipedia.org/wiki/Fitch_notation

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